Unintended pregnancies and use, misuse and discontinuation of oral contraceptives.

Unintended pregnancies are a recognized occurrence among women using oral contraceptives (OCs) as a consequence of both user and method failure. However, OCs also influence the occurrence of unintended pregnancies through an additional, poorly recognized, route: cessation of OC use by women who do not wish to become pregnant but stop using OCs because of side effects or other reasons. Many such women fail to immediately substitute a new contraceptive and/or adopt a less reliable contraceptive. This is a particularly important consideration for the approximately 3.7 million women who begin taking OCs in the United States each year since this group commonly experiences side effects and has a high discontinuation rate. Using a decision tree to follow a cohort of OC users over one year, we estimate that over 1 million unintended pregnancies are related to OC use, misuse or discontinuation. The greatest proportion of these, 61%, occur in women who discontinue OCs; of these, 66.6% occur in women who fail to immediately substitute other contraceptives and 33.3% because of the adoption of less reliable contraceptive methods. Of continuing OC users, the majority, exhibiting good compliance, contribute 24% of pregnancies because of their large numbers. Continuing OC users who are poor compliers, though many fewer, are responsible for 15% due to their high pregnancy rate. Unintended pregnancies in women who discontinue OCs account for approximately 20% of the 3.5 million annual unintended pregnancies in the United States, incurring costs of nearly +2.6 billion.(ABSTRACT TRUNCATED AT 250 WORDS)